This article reflects on the school's role in the building of citizenship, especially in socially vulnerable contexts. We argue, and try to show, that effective participation in decision-making processes is a key tool to promote conditions that help in social transformation and the formation of active citizenship. We offer a brief description of the current socio-educational scene, characterised by poverty and school failure, both emerging from the profound social, economic and cultural crises that affected Argentina in 2001. The resulting need for social integration, links between State and civil society, people's empowerment and political development make it necessary for the school to become an institution of community development, promoting opportunities for political socialisation and moral education. We describe a two-year action-research project in a secondary school in the north east of Argentina that aimed to enhance the bond between the school and the community and to democratise relationships in the school. Based on that experience, we critically analyse the way in which the school offers or denies opportunities for genuine participation and, as a consequence, the way in which the formation of citizenship is managed, and make some recommendations for rethinking the school from a social and political point of view. (Contains 12 notes.)